Walking beam conveyor



Oct 10, 1961 F` P. RUPPE WALKING BEAM coNvEYoR 4 Sheets-Sheet 1 Filed Feb. 9, 1959 Wm; R. m mp M mw 0, e a A P. R jm We Oct 10, 1961 P. P. RUPPE WALKING BEAM coNvEYoR 4 Sheets-Sheet 2 Filed Feb. 9, 1959 44 4z Huf INVENTOR.

Pfff-A? R PUPPE BY @mf/m @PM Oct. 10, 1961 P. P. RUPPE WALKING BEAM coNvEYoR 4 Sheets-Sheet 3 Filed Feb. 9, 1959 IN VEN TOR.

Pfff/v P. 9a/Pf ATTO/Mfrs Oct. lo, P P. RUPPE WALKING BEAM CONVEYOR Filed Feb. 9, 1959 4 Sheets-Sheet 4 INVENTOR.

Pfff/v f. Rapp: BY ,6a/alga, f /a/uv ATTORA/fy United States Patent() l 3,003,615 WALKING BEAM CONVEYOR Peter P.`Rup'pe, Grosse Pointe, Mich. Prab C onveyors, Inc., 30121 Groesbeek Highway, Roseville, Mich.) t

- Filed Feb. 9, 1959, Ser. No. 792,034

12 Claims. (Cl. 198-219) This linvention/relates to an apparatus for conveying articles. l

In general the articles to be conveyed are moved step by step along an article supporting surface, being lifted slightly off the surface during the movement and replaced on the surface during the pauses in the movement. To accomplish this, an article carrier reciprocates longitudinally of the supporting surface, being elevated relative thereto during movement in one direction to lift articles oi the surface and shift them longitudinally thereof, and being lowered relative to the supporting surface to replace the articles thereon during movement in the opposite direction.

The apparatus comprising the above-described general arrangement, and as hereinafter disclosed, includes a runway orfthe like along which the articles to be conveyed are moved, with an article carrier or walking beam so disposed vrelative to the article supporting surface of the runway that it will move from a position beneath such surface to an elevated position above such surface. Mechanism for reciprocating the beam longitudinally of the runway and for raising and lowering the beam serves to shift the beam, while elevated, in one direction and retract the beam, while lowered, in the opposite direction, with articles resting on the runway being raised therefrom and shifted therealong during the elevated shifting of the walking beam.

The articles are raised off the supporting surface of the runway only suiciently to clear such surface and prevent dragging of the articles as they are moved along the runway. In the embodiment herein disclosed the elevation of the walking beam Vis accomplished'by cam-like surfaces along and over which the beam is shifted during movement longitudinally of the runway. In one form of theinvention the cam surfaces are retracted to an inoperative position upon movement of the beam in one direction to allow longitudinal shifting of the beam in the lowered position, while in another embodiment the cam followers which cooperate with the cam surfaces are effective to raise the beam to an article supporting position as they traverse the cam surfaces during movement of the beam in one direction along the runway but are ineffective to raise the beam to an article supporting position during movement thereof in the opposite direction even though the followers ride over the cam surfaces. An object of the invention is the provision of apparatus for conveying articles whereby the articles are repeatedly raised from a supporting surface by an article carrier and shifted a short distance along the surface and then replaced on the surface with the article vcarrier being retracted along the surface below the articles to its starting position and again elevated to repeat the cycle. Ihe cycle is successively repeated to move the articles along the supporting surface in a step-by-step manner.

Another object of the invention is the provision of a relatively inexpensive, simple, and durable conveyor system for moving articles from one location to another.

Another object of the invention is the provision of a Other objects, advantages, and meritorious features will more fully appear from the specification, claims, and

accompanying drawing, wherein:

Mlee

FIG. l is a plan view of a conveyor system embodying my invention;

FIG. 2 is a cross sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a cross sectional view taken on the line 3--3 of FIG. 2 and showing the article carrier in the elevated position;

FIG. 4 is a cross sectional view taken on the line 3-3 of FIG. 2 and showing the article carrier in the lowered position;

FIG. 5 is a cross sectional View taken on the line 5 5 of FIG. 3 and showing the cams for elevating the article carrier and the mechanism for actuating the cams between operative and inoperative positions, and with the cams in the position to elevate the article carrier;

FIG. 6 is a cross sectional view taken on the line 5-5 of FIG. 3 and showing the mechanism disclosed in FIG. 5 but with the cams shifted to an inoperative position;

FIG. 7 is a cross sectional view taken on the line 7--7 i of FIG. 2;

FIG. 8 is a modification of the cam arrangement shown in FIGS. 5 and 6 to allow reversing of the conveyor system so that articles may be conveyed in opposite directions; and Y FIG. 9 is a modified form of the means for elevating the article carrier and showing cam followers which are operative to elevate the article carrier during its movement in only one direction longitudinally of the article supporting runway.

As shown in FIG. l the apparatus embodying the invention includes a pair of cooperating article supports, generally indicated at 20 and 22, having co-adjacent longitudinally extending article-supporting surfaces alternatively operative to support articles thereupon. Mechanism including means 24 is coupled with these supports to shift them longitudinally relative to each other. Such mechanism also includes means 26 adjacent opposite ends of the supports for raising one of the supports relative to the other during longitudinal shifting of the supports'in one direction and lowering the raised support during longitudinal shifting in the opposite direction,

Vwhereby articles A resting on support 20 are raised therefrom by support 22 and shifted along support 20 and lowered thereupon, with support 22 While lowered being returned to its starting position for repetition of the cycle, with the articles being thereby conveyed along support 20 in a step-by-step fashion. It will be apparent that a longitudinal end-to-end succession of the conveyor mechanism shown in FIGS. l and 2 might be provided whereby articles could be conveyed a substantial distance.

More specically, the support 20 serves as a runway or the like along which the articles to be conveyed are moved in the aforementioned step-by-step fashion. The runway, which may be supported in any convenient manner, not shown, includes a shallow frame (see FIGS. l-5) having longitudinally extending inwardly opening channel-shaped side frame members 28 and 30 extending the length of the runway and held in spaced parallel relation by floor means in the form of plates 32, 34, and 36 extending transversely therebetween and secured thereto in any suitable rigid fashion. The upper surfaces of iioor plates 32 and 36 provide, as hereinafter appears, article carrier-supporting surfaces or trackways supporting the article carrier for movement longitudinally of the runway. 'I'he upper flanges 38 and 40 of the side channels serve as article-supporting surfaces for the runway upon which the bottoms of the articles to be conveyed intermittently rest during movement along the runway. To complete the runway and conceal much of the operating mechanism of the conveyor, a wide article-supporting plate 42, whose longitudinal edges 44 are down turned "andspaced inwardly from complementary edges 46'and 3 48 of ilanges 38 and '40 'to 'provide slots through which `project the 'hereinafter-described walking lbeam, `entends' longitudinally of the frame along the center portion thereof and is supported coplanar with flanges 38 and 40 "by anglebra'ckets 46, '48; 50, and l52, 'as' shown in FIGS. 2 and 3. It is now apparent that except 'orthe Walking beam slots :in theupper `surface Aof 'the runway, the runway is substantially completely enclosed at the sidesand top. As such, it gives a nished 'appearance and prevents 'tampering with the mechanism housed therewithin, 'as well as preventing injury to personnel working adjacent theV conveyor. In addition, this unitary construction `allows 4installation lo'fthe'conveyor as ya'unit in anydesired location without the necessity of providing additional pulleys, shafts, guideways, etc., 'frequently 'associated with `'many otherforms 'of conveyors Extendingperiodicallyupwardly out ofthe slots formed r'between the edges '4'4lo'f center plate 42 andthe anges 38 and 40 are ithe 'article-lifting 'and Vconveying means, `speciiicallythe article carriers 54 and 56 which are 'the article-engaging portions of the walking beam mechanism. These vsupports are Aa lpair of parallel Vbars or vnarrow vertically arranged v'plates which 'extend 'longitudinally throughout substantially the entire length of the runway, terminatingshort-of'the ends-thereof as shown in FIG. l.

These carriers'are'disposed withinthewalking'beam slots and "are guided vfor v'longitudinal movement by Athe 'downturned edges 44, 46, and 48, which form the sides df the -slots. v*The uppered'ges or surfaces 'of these carriers 'serve "as article-lifting ksurfaces "for 'articles 'resting upon the article-supporting 'surfaces df the runway.

' 'The carriers are supported 'for reciprocatio'n longitudinally of the runway by roller means. More specifical- 'ly lreyfare-'supported 'upon a pair o'f fixed axles 5S and "60, -asbes't-'shownin FIGS. 1,y 3, and 5, Awith wheels v62 lvrotatably mounted on opp'ositeends oftheaxles. These wheels, which 'may "also be considered somewhat as ycam followers, 'roll upon 'the upper surfaces of the vfloor Lplates S2 and 36. To "ei'e'ct 'the longitudinal'shifting 'o'f 'thewalking beam'as wellas its Araising and'lowering, the 'means 24'and @2,6 heretofore mentioned is'disposedwithin 'the runway enclosure. Means 2'4i'nclutles, in fthe `illustrative 'embodiment shown, la 'uid -presure cylinder 64 .'pivotally connectedfas at66 to'the floor plate l34fandpro- 'vided with'acooperating piston "pivotally c'onne'ctedjto 'aibracket 70 extending'between 'and .secured to "the supports `54 "and "56 of the walking beam. -By 'alternate -'p'1e'ssurization of'opposite-en'ds'of'cylinder64, such as by an electrically "operated Huid pressure valve 65, under 5vthecontrl iof limit 'switchesSa and 65'b actuated by lingers 87a and 86asimilar to tlngers 'and 87 hereinafter mentioned, the valve 4'beingconnected to 'a source 'of iuid pressure, the piston68 will cause the fwalking.

'beam "to 'reciprocate longitudinally of the runway.

'As'the Walking beam reciproc'ates, me'ans26 serve to `raiseandiloweritrelative'to the article-supporting surface 'of the runway between'the 'position shown in FIG. 4 'wherein the upper surfaces "of suports 56 and "58 'are below the `article-supportingsurfacesfof the runway, .and the position shown 'in FIG. `3 where `the supports 'are elevated 'above the 'runway to 'lift an larticle therefrom :for .movement along the runway "spaced ther'ea'bova of 'the Upper surfaces of "floor .plates '32 `'and '36, 'or in 'other'words, the eective 'height of 'the article carriersupporting Vsurface over which `the carrierpasses during its reciprocation:longitudinally of the runway. `Means 26 includes four cams,.one `'for each `wheel 62. Three f the cams are shownin'FIGS. 2-5 .at 72, T4,.and 76. [The cams are laterallyV slidablel on their respective 'oorpla'tes 32 and 3'6fro`m operative ,positions in .which the wheel l'62 will roll overfthem vto raise .and Llower l.the walking serves, inelect, to raise .andlower'the e'iectiveheight- "beam, Lto 'inoperative ,positions outk ofthepaths .df the.:

of which is pivotally mounted respectiuely at 82 and 84 upon the floor plate 32. Because the cams must be oper- ;ative to raise the walkingfbeam duringi-ts imuvement in one direction and allow it to move in the oppositeirec- 1ltionwithout Vraising it, the shifting .ofthe cams fmust be "synchronized with `the -reciprocation Iof Lthe beam. lo -eiiect this lsynchronized movement, .alternately operative cam shift 'iingers 861and-87 '.aresecured, in any convenvient lfashion, at .longitudinally spaced apart :positions along -and -to one of the article .supports 56-to :strike the finger engaging .rollers .88 and 90 upstanding .respectively :from `arms -78 .and Bti to .pivot the .arms .between .the .positions ishown in FIGSLS and .6. lnzthelattergure'thercams ,'12 and 74 are sin .their inoperative positions.

With the walking beam moving in the direction .iof .armow .C in. FG..`S, '.thezwheels l62. arepassingvericams 72 and .74 .and the walking beamiisin ythe '.ele'vatediposition. t 5will be .apparent that .the walking beam :is V.held in .the :elevated position throughout the length :of thehigh apoint of thecams. The .cai-ns, asfshown.in.FIG. -2, f'are'.shaped :to 1have aupper .surfaces which "extend lengthwise :.of ;the direction :of emovement iof .the walking beam .with .such lupper surfaces having aa at iportion across :which zthe vwheels :62 will vroll .audit isfduring the travel of ,thewheels across such .flatelevated .suriacesofY the cams th'atthe neonveyingpf.articlesA is feiected. liesleugth ofitheiat .elevated surfaceof the cams need not befgreatibecause, by .continued reciprocation of the Awalking beam, Lthe articles will be moved in a uniform :step-by-stepmovement along the runway, and the lengthrof .the-.elevatedatporation of'the .cams will simply determine :.the:distance zthe .articles arermoved between the pausesin 1the..step.bystep .-mjovement -As wheels {62.ride1downfoff-thecams .and re- .turn'to the floor plateZ, -see FIG. 5, ,iinger186gstrikes pin .rollers 88 and 90 to swing cams 'l2 and 74 inwardly to-the FIG. .6 ,position `At this instant .the luid pressure Ato .cylinder T64 is redirected to enter .the-.opposite fend,A of .the .cylinder .and .the longitudinal Amovement .of vthe .Awal-king Abeamis reversed. .Becausethecams 72..and 7l4 have-been .retracted from thepath ofthe wheels. 62,-'.the walkingbeam -retracts without elevation. ..As piston .68..nears Ythexinward end .of its stroke and the wheels .62 have .passed 'beyond Acams 72:and 74, .cam actuating fingerstrikesthepin .rollers '.88 and 90 shifting the cams laterally-outwardly -back-into thepath of the wheels. Cylinder.64.at.this time is again Yreversely pressurized .and the .walking'beamreversesthe longitudinal movement. Wheels 62.ide up the cams 72 and 74 elevating'the walkingbeamtolift articles 'resting "on'the runway and to come therelong and again set them on'the runway as'the wheels run'tlown o'ffthe 'cams This 'cyclic `movement repeats 'itself 'in'.rhythmic fashion tomove'tlre articles A 'long'the'r way in a r-steplbyistepmanner.

-As'vthus farfdescrib'ed, Vthe conveyor will 1move Aarticles in-onlyone1direction along the `runway. VHowever, in La .modified form of i the i cam Lmechanism shown 4in :8, the conveyor may lbe' easily fadju-sted; to 1reversefth'e move- 'meut iof farticl'es thereon. Ywith the .lpreviously de yscribedembodiment, I two;pairs of' cams -areprovided.with thecamsrmounted.onpivoted pairsinf'arms,fonepair being sshown fat 92 -and 94 liii-FIG. t8 with .itcbeiugaunderstood y.that the cam :.mechanismnt .the otherfendtoftthe .walking beam is of identical construction except :hereinafter .mentioned .Arms .92 and ..94.aregpivoteduponlheoor .plate at 96 and 1.98. .A ,pin .roller .10.0 .ummm-.94amoperates with a slot 102 .in;the .companion :armaso uthat sposare the arms will shift synchronously.` An 'actuating Vrod V104 pivotally connected as at 106 to arm 92 extends longitudinally ofthe runway just beneath the center plate 42 and is pivotally connected at its opposite end to an arm, of the other pair vof arms, corresponding to farm '92. As thus Vfar described, the cam mechanism coupled to opposite ends of red 104 are identical and-upon Vactuation of the cam arms 92 and 94, the rod 1'04 cause corresponding movement of the other pair of arms at the 'opposite end 'of the runway.

Arm 92 is provided with a 'slidable reversing plate 108 having slots therein through `which bolts 1-10 and 112 slidably connect the plate to the arm. A handle 114 is rigidly connected -to the plate and projects outwardly through the side of the runway through a slot 116. Upstanding from the reversing iplate lare two arm shifting pins 118 and 120. Secured in any convenient fashion at longitudinally spaced-apart points -to opposite sides of the carrier 56 are two pairs 0f cooperating cam arm actuating tingers, one pair being indicated lat Y122 and 124, and the other pair at 126 and 128. Fingers 122 and 124 cooperate with arm shifting pin 120 to elect actuation of cam arms 92 and 94 so that articles are conveyed along the runway in the direction of arrow D while ngers 126 and 128 cooperate with pin 118 to cause the walking beam to move articles along the runway in the 4direction of arrow E.

The operation of the FIG. 8 modification may be visualized from consideration of, inst, the solid outline position of the arms 92 and 94, and thereafter a consideration of the phantom outline of the arms. In the solid outline the reversing plate 108 is shown in its slidable position on the arm 92 so that articles will be shifted in the direction of arrow D. The iinger 122 has ust struck pin 120 with the supports 56 and 54 moving in the direction of arrow D to swing the cams 72 and 74 inwardly and out of the path of the wheels 62. Reverse movement of carriers 54 and 56 will now occur without elevation thereof. Once the wheels 62 have passed beyond the ends of cams 72 and 74, actuating nger 124 will strike pin 120 to swing the arms 92 and 94 outwardly to position the cams in the path of the wheels 62. Thereafter, upon movement of the carriers 54 and 56 in the direction of arrow D, the carriers will be elevated and the articles will be moved along the runway in the direction of arrow D.

To reverse the movement of the articles on the conveyor, and assuming that the carriers are in the positions shown in FIG. 8, the operator grasps handle 114 and through a combined swinging and pushing of handle 114 in the direction of and corresponding to the shape of arrow F, he swings the arms 92 and 94 radially outwardly to the phantom outline position shown. During this swinging movement and inward pushing of handle 114, the reversing plate 108 is shifted inwardly so that the pins 118 and 120 assume the phantom outline positions indicated at 1181 and 1201. It will be noted that the phantom outline position of pin 120 is disposed inwardly and out of the path of movement of actuating ngers 122 and 124, while pin 118 in its phantom outline position 1181 is in the path of movement of fingers 126 and 128.

Assuming that the supports now move in the direction of arrow E, wheels 62 will ride up over cams 72 and 74 shown in phantom outline at 721 and '741 to elevate the supports and shift the articles in the direction of arrow E. Near the end of the stroke of the supports, finger 128 will engage pin 118 in its phantom position 1181 to swing arms 92 Vand 94 inwardly and through rod 104 to cause corresponding movement of the cam arms at the opposite end of the walking beam. Thereupon reverse movement of the supports in the direction of arrow D will allow the supports to return to the positions 'shown in FIG. 8 without elevation and when finger 126 strikes pin 118 in its 'phantom outline position, lthe arms 92 and 94 will be "swung to 'thephantom outline position to dispose cams i" artioleson the runway.

72 and 74 at the position 721 and 741. Itis now apparent that articles will be moved along the runway in the direction of arrow E.

Shown in FIG. 9 is a 'further modication of the invention. This modification overcomes the necessity of laterally 'shifting the cams out `of the path of the Wheels 62 in order to prevent elevation of the'walking beam during movement in one direction. In this modication the Vwheels 62, heretofore mentioned in connection with FIGS. 1-8, linstead 'of being lmounted in fixed relation with supports 54 and 56, are connected thereto by swinging links. The 'wheels are indicated in two different positions, a lowle'vel 'position at 162 and a high-level position at 1621 in FIG. .9. They are mounted in pairs as heretofore described at opposite ends of axles, one of the axles being shown in FIG. 9 at 158. The axles are connected to the carriers 54 and 56 by pairs of swinging links, one of which is shown at 164, being pivotally connected to the supports as at 166. The supports are provided with cutouts in the form of rectangular notches 168 and the axle 158 is capable of swinging about its pivotal connection 166 between the position shown in solid outline at the left in FIG. 9 and the position shown in phantom outline. The elevating cam 170 over which the wheel 162 rides is provided with the at upper Vsurface 172 corresponding to the ilat surface heretofore mentioned in connection with cams 72 and 76. However, cam 170 has dilerent angles of approach at opposite ends. The approach angle at the left and indicated at 174 is not as steep as the approach angle at the opposite end indicated at 176. These different approach angles at opposite ends of the cam together with the pivotal connection 166, being disposed more closely adjacent theend 178 of notch 176 than it is relative to the end 180 of the notch, serve to cause swinging of the wheel axis 158 between the solid and phantom positions.

The cams 170 serve in eiect to provide the carriersupporting surfaces of the door plates 32 and 36 with a highelevel portion 172 and a low-level portion 183. 'Ihe notches 168 serve as means limiting the pivotal swinging movement'of the wheel links 164.

Assuming that the walking beam has finished its movement in the direction of arrow F of FIG. 9, and starts its movement in the direction of arrow G, the wheel 162 will engage the step 182 at the end of cam 170 and the resistance to rolling movement otered by the step will cause the link 164 to swing from the phantom position shown in FIG. 9 to the solid position. As the movement of the walking beam continues in the direction of arrow G, wheel 162 will ride up over the cam 170 and down the inclined surface 176. During such movement the upper surface 184 of the walking beam will be disposed below the article-supporting surface 186 of the runway. However, upon movement of the walking beam in the direction of arrow F, the resistance olered wheel 162 by the steep slope 176 of the cam will canse the axle 158 to swing from the ysolid outline position Ato the phantom outline position indicated at 1581. The walking beam Hwill now be disposed with its supporting surface 1841 dis- .tion of arrow G will, as heretofore mentioned, cause the axle to swing from the phantom outline position to that of the solid outline position lowering the walking beam so 'that its return movement will be inetective to move the What I claim is:

1; An article conveyor comprising, in combination: an article support having an article-supporting surface over -which articles to be conveyed are moved; mechanism for shifting articles along said support including an article carrier reciprocable longitudinally of said support in the direction of article movement and having an article-lifting surface'disposed beneath articles to be moved along ,the support; means providing an article carrier-supporting surface extending in the direction of carrier movement and upon which the carrier is supported for reciprocation; said carrier-supporting surface so disposed relative to the article-supporting surface of said support Ithat the article-lifting surface of the carn'er is disposed .beneath the article-supporting surface 'of said support;

cam means shiftable relative to the first-mentioned means between a position in the path of carrier movement to elevate the carrier and dispose its article-lifting surface above the article-supporting surface of said support, and a position retracted from the path of the carrier; and actu- -ating means coupled with said cam means and with said mechanism and operative to synchronize functioning to shift said cam means to a position in the return path of Ythe carrier atthe end of one stroke thereof and retract the cam means from the path of the carrier at the end of such return stroke.

2. The invention as defined in claim l characterized in Athat the rst-mentioned means is dened by a portion of said support disposed spaced below the article-supporting surface of said support .and Yextending longitudinally thereof.

3. An article conveyor comprising, in combination: an

-article support having a longitudinally extending articlesupporting surface providing a -runwayralong which articles to be conveyed are moved; an elongate article .carrier extending longitudinally of said runway; means providing a carrier-supporting'surface for supporting said lcarrier .for reciprocable movement Vlongitudinally of the runway with the upper surface of the carrier disposed below the runway; cam means supported for shiftable vage coupled to said cam means and operatively .coupled with the carrier to be actuated at each end of each stroke of carrier reciprocation longitudinally of the runway to shift the cam means from one of said positions to the other; and drive means coupled to the carrier for reciprocating it. Y

4. The inventionias defined in claim 3 characterized in that said actuating linkage includes a portion engageable by the carrier as the carrier reaches each end of its stroke and which portion serves to actuate said linkage in first one direction and then the opposite direction, and said portion being mounted on the linkage for shiftable movement relative thereto between two positions causing actuation of the linkage respectively in one direction or the other at the same end of the carrier stroke to provide reversal of article movement by the conveyor.

5. An article conveyor comprising, in combination: an elongate at article-supporting surface extending in the direction of intended article movement; a pair of article carriers, one at each side of said'surface, with each carrier having an elongate article-lifting surface extending along the length of said article-supporting surface; means coupled to said carriers to reciprocate them longitudinally of the supporting surface; means providing carrier-supporting surfaces upon which the carriers are supported for said Vreciprocating movement; cam means shiftable '-across'the carrier-supporting surface between positions elevating the `carriers as they engage and ride over'ethe cam means to dispose said article-lifting surfaces of the carriers above said article-supporting surface, and positionspout of the path of carrier movement to allow carrier movement longitudinally of said supporting surface with-.the article-lifting surfaces of the carriers disposed below said article-supporting surface; and means coupled to said cam means and cooperable with the carriers to synchronize shifting of the cam means with the reciprocation of the carriers. d

6. An article conveyor comprising, in combination: a pair of elongate at article-supporting surfaces extending in the direction ofv intended article movement; a pair` of article carriers, one adjacent each of said surfaces and each having an article-lifting surface extending in the direction of thelength of said supporting surfaces; means coupled to said carriage to reciprocate them longitudinally of the supporting surfaces; means providing longitudinally extending carrier-supporting surfaces upon which the carriers are supported for said reciprocating movement; cam means shiftable across the carrier-supporting surfaces between positions elevating the carriers as they engage and n'de over the cam means to dispose the article-lifting surfaces thereof above said article-supporting surfaces, and positions out of the path of carrier movement to allow carrier movement longitudinally `of said supporting surfaces with the article-lifting surfaces disposed below said article-supporting surfaces; and means coupled to said cam means and cooperable with the carriers to synchronize shifting of the cam means with the reciprocation of the carriers. i

7. An article conveyor comprising, in combination: a -pair of parallel elongate channel-shaped members each Yliaving an upper flan-ge with the members spaced apart along :their lengths and said anges disposed in horizontal coplanar relation and providing a pair of articlesupporting surfaces along which articles to be conveyed aremoved; floor means extending lbetween and secured to said members adjacent opposite ends thereof and disposed. spaced below said article-supporting surfaces; article-lifting and conveying means having an article-lifting surface disposed between and extending longitudinally of said members and normally disposed below said article-supporting surfaces; mechanism coupled with said article-lifting and conveying means to reciprocate the same longitudinally of said members; a plurality of roller means secured to the lifting and conveying means and Vsupporting the same for movement across said floor means; a plurality of cams, one for each roller means, slidable across said floor means into and out of the path Vof lthe roller means during reciprocation of the article- 'lifting and conveying means, an -arm for each cam shiftably mounted on the oor means and secured to its respective cam to shift the cam as aforesaid; actuating means carried by said lifting and conveying means and cooperable with said arms at one end of each stroke of the lifting and conveying means to shift the cams into the path of the roller means for the ensuing reverse stroke and cooperable with the Iarms at the opposite Vend of each stroke of the lifting and conveying means to shift the cams out of the path of the roller means for the ensuing reverse stroke.

8. The invention as defined inclaim 7 characterized in that said lifting and conveying means includes a pair of elongate article carriers disposed in parallel spacedapart relation between said members and having at horizontal coplanar article-lifting surfaces, and a cover plate is disposed between the carriers and extends along the length of said members coplanar with the flanges of said members and secured in ixed relation relative thereto Yand covering and concealing the cams and roller means tively shiftable between positions to engage one .or the other of said sets of actuating ngers, one set of said ngers operable to shift the arms in one direction at the end of each stroke of the conveying and lifting means and the other set operable to shift the arms in the opposite direction at the end of each stroke whereby the direction of article movement by the conveyor may be reversed.

10. A step-by-step article conveyor comprising, in combination: a generally planar article-supporting surface along which `articles are to be conveyed, mechanism for shifting articles along said surface including an article carrier reciprocable along said supporting surface beneath articles resting upon such surface; a rst carrier- Supporting surface upon which the carrier rides during reciprocation in one direction and so disposed relative to the article-supporting surface that the carrier is in a noncarrying position beneath articles on the article-supporting surface; a second carrier-supporting surface upon which the carrier rides during reciprocation in the opposite direction and which is disposed above the rst car-Y rier-supporting surface such that the carrier is in an article-carrying position above the article-supporting surface; and means coupled with one of said carrier-supporting surfaces and cooperable with said mechanism to shift such surface into and out of the path of carrier reciprocation at the completion of successive strokes of reeiprocatory travel of the carrier.

l1. A step-by-step article conveyor comprising, in combination: an elongate runway surface along which articles are to be conveyed; an article carrier; means supporting said carrier beneath articles resting upon said runway for reciprocation in the direction of intended article movement along the runway; a rst carrier-supporting surface cooperable with said means during reciprocation of the carrier in one direction and so disposed relative to the runway surface that the carrier is supported in a noncarrying position beneath articles resting on the runway; a second carrier-supporting Surface cooperable with said means during reciprocation of the carrier in the opposite direction and vertically displaced from the first carriersupporting surface and so disposed relative to the article runway that the carrier is supported in an article-carrying position above the runway; and mechanism coupled with one of said carrier-supporting surfaces and responsive to reciprocation of the carrier to shift such surface to a position cooperable with said means prior to reciprocatory movement of the carrier in one direction and shift such surface out of a position cooperable with said means prior to reciprocatory movement of the carrier in the opposite direction.

12. The invention as defined in claim 11 characterized in that said mechanism includes a part shiftable independently of the carrier to reverse operation of such mechanism whereby the said one carrier-supporting surface is shifted out of a position cooperable with said means prior to reciprocation of the carrier in said one direction and is shifted to a position cooperable with said means prior to reciprocation of the carrier in said opposite direction.

References Cited in the le of this patent UNITED STATES PATENTS 2,400,763 Malo May 21, 1946 2,622,401 Drago Dec. 23, 1952 2,940,490 Himmelheber June 14, 1960 

